1. Field of the Invention
The present invention relates to a non-volatile memory apparatus. More particularly, the present invention relates to a non-volatile memory apparatus configured to prevent from read disturb and an accessing method thereof.
2. Descriptions of the Related Art
Non-volatile memories are widely used in many digital products such as mobile phones, personal computers, MP3 players, PDAs (personal digital assistant) and digital cameras. However, there are some limitations due to the natural characteristics of non-volatile memories. For example, a flash memory may repeatedly read the same block in the flash memory when data stored in the flash memory is static, that is, not erased or moved. Since the block is mainly constituted by a plurality of transistors, once the block is in static situation, the electric potential voltage on the floating gate of a transistor would vary. For a NAND flash memory, the electric potential voltage would increase when the block is static for a long time. More particularly, for a NAND flash memory, electrons flow out of the floating gate when the NAND flash memory is read, causing an increase in the electric potential voltage. In other words, the various electric potential voltages may have an error when the block is read again. The aforementioned phenomenon is denoted as a read disturb, and the flash memory cannot be read correctly. Moreover, the data may be lost and cannot be retrieved anymore.
Thus, it is important to modify data blocks that are read extortionately to prevent read disturb.